Vapor generator and superheater



March 31, 1953 c. H. WOOLLEY 2,633,109

VAPOR GENERATOR AND SUPERHE'ATER Filed June 23, 1949 I8 INVENTOR Ch ar/esHWool/ey F/ 1 QWTQRNEY Patented Mar. 31 1953 VAPOR GENERATOR AND SUPE'RHEATER Charles H. Woolley, Cranford, N. J assignor to The Babcock & Wilcox Company, Rockleigh, N. J., a corporation of New Jersey Application June 23, 1949, Serial No. 100,854

The present invention relates to a vapor genferating installation which will be exemplified herein as a water tube steam generator of the radiant'jtype. The main object of the invention is the provision of a vapor generator of "the radiant type which is particularly characterized by its high steam generating capacity relative to the fioor space occupied by the installation.

A further object of the invention is the provision of a vapor generator of the character described which is particularly adapted and specially designed for the burning of pulverized solid fuels at relatively high rates of heat release without danger of fouling the surfaces of the convection section of the installation by slag constituting. the incombustible residue of such fuels.

Another object of the invention is a vapor generator characterized'by low construction costs and low maintenance.

More specifically the invention involves the provision of a vapor generator including a large volume fluid cooled furnace fired by pulverized fuel burning means, the position of fuel introduction and the position of the exit of the products of combustion from the furnace being such that ash particles released by combustion are cooled in their downward flow and are deposited in a subjacent space.

The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, its operating advantages, and the specific objects attained by its use, reference should be had to the accompanying drawings and descriptive matter in which there 'is illustrated and described a preferred embodi- Inent of the invention.

In the drawings;

' 1 is a vertical section; and i Figs. 2 and 3 are detail horizontal sections on the lines 2-2 and 3-3 of Fig. 1. r

The drawing discloses a vapor generating installation having a vertically elongated furnace or co'mbustioncha'mber Ill the boundary surfaces of whichare mainly defined by vapor generating tubes communicating with the vaporand liquid drum l2. One such boundary surface is shown at l4 as defined by the wall tubes 16 extending from the lower header [8 to the upper. header 2llwhich, in turn, is connected bythe roof .defining tubes 2| to the drum l2. The rear wall 24 is definedf at least in part by downcomer tubes 26 extending from the submerged lower drum'28 aiid connected to the lower header j he re- 3 Claims. (01. 122-336) maining upright walls of the combustion chamber are similarly defined by upright vapor generating tubes such as those indicated at 32 having their lower ends connected to the lower header 34. The upper ends of all of the steam generating tubes are in communication with the steam space of the drum l2'through appropriate headers and tubes, and the lower ends of the tubes are, for the purposes of natural circulation, in communication through headers such as I8, 30, and 34, and their appropriate connections with the lower drum 28.

In addition to the downcomers 26 which are connected to the header 30, the latter has connected thereto the lower ends of steam generating tubes 36. The lower parts of these tubes extend along the wall 24 and their intermediate parts form the tubular screens 38 and 40 extending across the gas inlet 42 of the gas pass 44 0f the convection section. The upper parts of these steam generatin tubes define the division wall 46 and beyond this wall these tubes continue to a point of connection with the drum.

At a position above the tubular screens 38 and 40, there is an auxiliary heater exemplified by a high temperature superheater section consisting of a bank of tubes 48. This bank of tubes is formed by a plurality of return bend sections connected in series and having corresponding inlet ends connected to the inlet header 50, and their opposite ends connected to the outlet header 52.

Above the high temperature superheater section 48 is a low temperature superheater section .56 includingsuperposedbanks of tubes 51 and 58v formed by series connectedreturn bend sections. The inlets of these sections are connected by tubes such as 60 and 62 to the steam spaceofthedruml2. v

Steam flows from the outlet header 66 of the lower temperature superheater section 56 through an external tubular connection 10 to a tubular junction member 12 which mayhave therein; a valve such as. 14 pivotedat' l6 and controlled from steam flow from the-header 52 and from the temperature ofthe steam leaving the header 66, to divide and variably proportion the flow of steam'between the tubular :.connection'8l! and a bypass connection- 82;- p e The tubular connection leads to an attemperator which may-include-a bundle of tubes such as shown at 84,- submerged in the-drum 28. The

through the tubular outlet connection 86 to a pointof junction 88 with the bypass connection 82. From this point the mixed steam flows to the header 50 and thence through the tubular sections of the high temperature superheater section 38 to the outlet header 52 and thence to a point of use. The attemperated steam is mixed with the bypassed steam in passing to the header 50 and the final temperature of the steam is thus controlled and maintained within permissible limits.

The furnace gases flowing upwardly from the superheater sections turn at the upper end of the gas pass M and pass across the elements of two banks of tubes such as thoseindicated at 90 and 92. These tubes directly connect the drums l2 and 28.

After passing across the bank of tubes :02 the gases flow upwardly through the duct .or flue 9.4 to a regenerative air heater 96, and the combustion air heated thereby flows from the air heater 90 through ductwork 98 to an enclosure I from which secondary air is supplied to the burners such as 192 and .404. These burners,-;as indicated by the drawing, effect downward .firing of the furnace to, and when pulverizedcoal-is used as fuel, the temperature of the furnace gases and particles of ash suspended therein is sufliciently lowered by the furnace wall tubes to prevent fouling of the surfaces of theconvection super- ,heaters within the gas pass (is.

To attain high superheated steam-temperatures and yet provide a unitwhich may be started :up with a minimum hazard to the superheater located close to the furnace gas outlet, the superheater elements are arranged horizontally so that they may be drained or blown-out before or during the starting .up period.

The zone of hi h temperature in the furnace is at the top but the furnace is elongated in its vertical dimension, and the down-firing burners are so distributed that when all burners are in operation the products ofcombustion pass downward and are cooled to anadequate ash temperature by the time they are directed in a 180 turn above the front to back hopper and enter the vertical superheater pass.

The illustrative installation provides :a combined unit which is inherently simple in construetion, rugged and durable in operation, andreadily cleanable.

The construction is :free of baiiies confined locations and no short gas turns are involved, :so that uniform heat transfer conditions result with respect to hi h temperature heat absorbing rsur- Iaces, makingior better utilization oithesurfaces in attainin maximum heat absorption rates.

The furnace and convection :pass construction is simple, the side walls involving the upper and lower headers, such as 34' :and 23:4, extending at the same elevation from the front wall to the rear wall, with provision of :an intermediate junction header 35' at a oositionnear the :upper art of the high temperature superheater section, .so that more widely spaced side wall tubes so .are used in the-upper portion of the superheater pass and the gas turning space :83 forwardly of the saturated boiler bank.

The gas collecting chamber .93 .rearwardly of the saturated bank is shown :as connected for gas delivery to the air heater located above the unit. when the plant design is such that the stack is supported at ground level, or when :it is advantageous to arrange the fan at such a low level,

then the gas outlet to the air heater may be arranged rearwardly, or downwardly from the chamber 93.

In the particular form of the invention shown by the drawing, it is to be noted that the inlet tube sections 60 and 62 of the low temperature superheater section pass downwardly on the forward side of the gas turning space 89, then angle across the upilowing gas stream to a position below the submerged drum 28. These sections thus present heat absorbing surfaces and are arranged to provide for expansion between the position where they pass through the upper roof section 9! and where they connect to the super- .heater-seotionififi. They are preferably supported on the walls of the superheater pass.

."Iihe :illus'tratiue :installation has an operating pressure 10f 2875 g). s. i. and a peak capacity of l5'0,00'0 pounds per hour. Its total steam temperature is 915 .F. at a 25,000-450,000 steam capacity range. Its feed water temperature is 3.85" F. at 450,000 pounds per hour.

In the illustrative installation, wall tubes of the furnace ill .areelosiely spaced or contiguous tubes, as indicated .in ,Fig. .2 of the drawings, with the .sidesof the tubes full-y exposed to the furnace.

The installationalso includes the two-drum and saturated :tube bank arrangement involving components 4:2, :23, .90 and .92, "with downcomers 26 leading to the lower :furnaee wall headers such as i8, 30, and at, shielded .;by the risers, or steam generating tubes With this arrangement, the supply of vaporizable liquid :to thefurnace walls .is .irom thelower drum .2 8.. The circulating characteristics of the unit, and particularly the two- .saturated bank :of tube arrangement, are

such that the liquid supply for the "furnace walls may usually be taken from the lower drum.

The supply :of iliquid to the :tubes defining the furnace walls is from the upper steam and water drum 1% through the saturated bank or" tubes 92, the lower drum 28 and the shielded downcomer tubes :26, While the-adjacent ends of the tubular elements of the bankszof superheater tubes is are supported by the downcomertubes 20, the latter being pendently supported from the lower drum .28

All the tubes and headers, comprising the satimitated steam structure, are supported from a common top level represented by the beam I03 so that all of the elements of that structure expand downwardly together. Pendent supports connect the uppersteelwork,represented by the beam 103, with the saturated elements. Examples of such pendent supports :are indicated at lob, I01, and

The lower firont wall header I B and the side wall headers 34 are supplied with vaporizable liquid by direct extensions, such as 1 lo-! M, of some of the downcomer tubes 26 or by junction connectors from the header 30. I

While in accordance with the provisions of the statutes there has been illustrated and described -a preferred form of the invention, those skilled in the art will unders'tand'that changes may be made in the form :of the-apparatus disclosed without departing from the spirit of the invention as 7 indicated by the subjacent claims, "and that certain features of the invention may sometimes be used to advantage without a corresponding use of other features.

Whatis claimed is: Y

1. In a vapor generating unit, a furnace the walls of which are defined by upright vapor generating tubes, burner means for firing saidfurlnace at its upper part, some of said tub es definingan upright wall common to the furnace and an upright gas pass disposed-alongside the upper portion of the furnace and having a gas inlet communicating with the lower part of the furnace, parts of the last mentioned wall tubes being disposed as horizontally inclined screen tubes extending across the gas pass gas inlet to the rear wall of the furnace, an elevated vapor and liquid drum adjacent the top of the gas pass, a liquid drum at a level beneath that of the vapor and liquid drum, but intermediate the height of the gas pass, a bank of upright fluid heating tubes directly connecting said drums and disposed transversely of gas flow from the upper part of the gas pass, means connecting the vapor discharge ends of said vapor generating wall tubes with the vapor and liquid drum, downcomer means for connecting the inlet ends of the vapor generating wall tubes with said liquid drum, a superheater including a bank of vertically spaced horizontally disposed tubes extending transversely of the flow of gas in the lower part of said gas pass and in proximity to said screen, means connecting the vapor space of the vapor and liquid drum to the inlet of the superheater, and hanger means pendently supporting said drums and said bank of tubes, said downcomer means including downcomer wall tubes extend ing downwardly from said liquid drum along the rear wall of the gas pass and the subjacent rear wall of the furnace, said downcomer tubes being also pendently supported by the liquid drum and being thermally protected at their lower portions by a row of lower parts of the common wall vapor generating tubes disposed between the downcomers and the interior of the furnace.

2. In a vapor generating unit, a furnace the walls of which are defined by upright vapor generating tubes, burner means for firing said furnace at its upper part, some of said tubes defining an upright wall common to the furnace and an upright gas pass disposed alongside the upper portion of the furnace and having a gas inlet communicating with the lower part of the furnace, parts of the last mentioned wall tubes being disposed as horizontally inclined screen tubes extending across the gas pass gas inlet to the rear wall of the furnace, an elevated vapor and liquid drum adjacent the top of the gas pass, a liquid drum at a level beneath that of the vapor and liquid drum, but intermediate the height of the gas pass, a bank of upright fluid heating tubes directly connecting said drums and disposed transversely of gas'fiow from the upper part of the gas pass, means connecting the vapor discharge ends of said vapor generating wall tubes with the vapor and liquid drum, downcomer means for connecting the inlet ends of the vapor generating wall tubes with said liquid drum, a superheater including a bank of vertically spaced horizontally disposed tubes extending transversely of the fiow of gas in the lower part of said gas pass and in proximity to said screen, steam supply tubes connecting the vapor space of the vapor and liquid drum to the inlet of the superheater and having parts disposed within the gas pass between the superheater and said bank of tubes, and hanger means pendently supporting said drums and said bank of tubes, said downcomer means including downcomer wall tubes extending downwardly from said liquid drum along the rear wall of the gas pass and the subjacent rear wall of the furnace, said downcomer tubes being also pendently supported by the liquid drum and being in communication with the interior of that drum.

3. In a vapor generating unit, a furnace the walls of which are defined by upright vapor generating tubes, burner means for firing said furnace at its upper part, some of said tubes defining an upright division wall common to the furnace and an upright gas pass disposed alongside and rearwardly of the upper portion of the furnace and having a gas inlet at its lower end communicating with the lower part of the furnace, parts of the division wall tubes being disposed as horizontally inclined screen tubes extending rearwardly from said division wall across the gas pass gas inlet to the rear wall of the furnace, an elevated vapor and liquid drum adjacent the top of the gas pass, a liquid drum at a level beneath that of the vapor and liquid drum but above the screen tubes and said rear wall of the furnace and intermediate the height of the gas pass, a natural circulation bank of upright fluid heating tubes directly connecting said drums and disposed transversely of gas fiow from the upper part of the gas pass, means connecting the vapor discharge ends of said vapor generating wall tubes with the vapor and liquid drum, downcomer means for connecting the inlet ends of the vapor generating Wall tubes with said liquid drum, a superheater including a bank of vertically spaced horizontally disposed tubes extending transversely of the flow of gas in the lower part of said gas pass and in proximity to said screen at a position substantially below the level of said liquid drum, the superheater also including header means disposed exteriorly along the rear wall, means connecting the vapor space of the vapor and liquid drum to the inlet of the superheater, and hanger means pendently supporting said drums and said bank of tubes, said downcomer means including downcomer wall tubes extending downwardly from said liquid drum and pendently supported thereby.

CHARLES H. WOOLLEY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,898,079 Cross Feb. 21, 1933 2,196,889 Bailey Apr. 9, 1940 2,206,265 Saathoif July 2, 1940 2,222,769 Hardgrove Nov. 26, 1940 2,254 226 Koch Sept. 2, 1941 2,278,798 Hardgrove et a1. June 30, 1942 2,287,798 Hardgrove et al. June 30, 1942 2,498,761 Kuhner Feb. 28, 1950 2,537,042 Fink Jan. 9. 1951 

